1. Field
The present disclosure generally relates to the fabrication of stiffened composite panels, and deals more particularly with a method and apparatus for forming, assembling and curing stiffened skins using configurable modular tooling.
2. Background
In order to strengthen and stiffen composite panels such as aircraft wing skins, the panels may incorporate composite stiffeners. For example, aircraft composite wing skins may be stiffened with composite stringers that extend in the span-wise direction of the wing and are attached to the skin by bonding or co-curing techniques.
Existing tooling used to cure stiffened skins is typically large, heavy and expensive to fabricate. The skins are laid up directly on the cure tool along with the stringers and then vacuum bagged. The placement and assembly of the stringers, skin, bagging and related items are performed serially, resulting in relatively long work-in-process (WIP) flow times. Because of these long flow times, multiple identical tool sets may be required to achieve desired production rates. These additional tool sets increase both capital costs and factory floor space requirements. Furthermore, additional cure tooling and associated special tools are also typically required to layup, handle, protect and accurately index the stringers when they are being installed on a skin. These additional tools may also be large and expensive, further adding to capital costs, tooling lead times and floor space requirements.
Another problem with existing tooling is related to the need to install vacuum bagging over the stringers and skin after they have been laid up. This requires that the panel be fully assembled before bagging can be installed, consequently bagging flow time becomes part of the critical production path.
Accordingly, there is a need for a method and apparatus for fabricating stiffened composite panels, such as wing skin panels, that reduce tooling and related floor space requirements, and which increases production flow rates. There is also a need for a method and apparatus of the type mentioned above, which allows parallel processing of layup, bond assembly and bagging operations in order to reduce the amount of WIP and tool turns.